How to Compute a BMI

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By an eHow Contributing Writer

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BMI stands Body Mass Index. It is a formula used to estimate an individual's body fat constitution. The most popular formula calculates BMI based on an individual's height and weight. Medical professionals use this figure to assess health risks associated with obesity and being overweight. And while this BMI formula does not measure body fat directly, and is given to some inaccuracies, it is a reasonably reliable and inexpensive way to quickly evaluate physical fitness.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

Calculator

Calculating your BMI using the computer

Step 1

Use the BMI resource at the end of this article. (Res. 1.)
Step 2

Select the calculator that fits your need (for adult, teen, or child).
Step 3

Enter the information for your height in feet and inches, and weight in pounds. Then select calculate.

Calculating your BMI by hand

Step 1

Write the following formula, filling in the appropriate figures:

[Weight in pounds / (Height in inches)2] x 703 = BMI.
Step 2

Use your calculator to resolve the equation.
Step 3

Interpret the results.
If you're an adult and your BMI is below 18.5, you are considered underweight.
If you're an adult and your BMI is between 18.5 and 24.9, you are considered normal.
If you're an adult and your BMI is between 25.0 and 29.9, you are considered overweight.
If you're an adult and your BMI is above 30, you are considered obese.

Tips & Warnings

The same formula is used to calculate BMI for both children and adults. However, the standard for interpretation is different for a person under 20 years old than it is for a person over 20 years of age. Because the amount of body fat changes with age and varies between girls and boys, the BMI interpretation for children and teens is age- and sex-specific.
Your BMI value, in conjunction with your waist measurement and other risk factors (such as family history and cigarette smoking), is used to assess your overall risk of developing obesity-related diseases. In women, a waist measurement greater than 35 inches, combined with a high BMI, increases the danger of developing health complications. In men, a waist measurement above 40 inches, combined with a high BMI, increases the danger of developing health complications.
Being overweight or obese is associated with an increase risk of heart disease, stroke, some forms of cancer (such as breast and colon cancer), Type 2 diabetes, hypertension, and elevated cholesterol, among other risk factors.